Welcome to The Forum, The first thing I would check would be the battery, If it is going bad all kinds of crazy things can happen, check and clean the connections first, check the voltage it should be 12.7 if fully charged, if you have any doubts have it load tested:s

don't know if this will apply to a 08 model , but my 96 speedo will go crazy , quit working , all kinds of weird things . My problem was/is in the key switch . I could wiggle the key and it would straighten up .i got to get another switch but in the meantime , I just wiggle the key when it acts up and it goes back to working right